Cooling apparatus, semiconductor module, and vehicle

ABSTRACT

A semiconductor module is provided, where a coolant circulation portion of a cooling apparatus has a first coolant flow channel and a second coolant flow channel arranged so as to sandwich therebetween a fin region in which a cooling fin is provided, and each having two ends in a longitudinal direction, a casing portion of the cooling apparatus includes a first opening provided on an end side corresponding to a first end of the first coolant flow channel and a second opening provided on an end side corresponding to a second end of the second coolant flow channel, the second end and the first end are arranged on the same side of the casing portion, and the first coolant flow channel and the second coolant flow channel are each at least partly provided below the cooling fin.

The contents of the following Japanese patent application(s) areincorporated herein by reference:

NO. 2018-070713 filed in JP on Apr. 2, 2018.

BACKGROUND 1. Technical Field

The present invention relates to a cooling apparatus, a semiconductormodule, and a vehicle.

2. Related Art

In the prior art, it is known that a cooling apparatus is provided in asemiconductor module including semiconductor elements such as a powersemiconductor chip or the like (for example, see Patent Documents 1-8).

Patent Document 1: WO 2014/69174

Patent Document 2: WO 2013/157467

Patent Document 3: WO 2015/178064

Patent Document 4: Japanese Patent Application Publication No.2017-84978

Patent Document 5: WO 2015/93169

Patent Document 6: WO 2013/54887

Patent Document 7: WO 2006/118032

Patent Document 8: Japanese Patent 5206102

SUMMARY

A cooling apparatus preferably has a high cooling performance.

To solve the above-mentioned issue, according to a first aspect of thepresent invention, provided is a semiconductor module including acooling apparatus and a semiconductor device. The semiconductor devicemay include a semiconductor chip. The cooling apparatus may include atop plate having an upper surface and a lower surface, where thesemiconductor chip is arranged above the upper surface. The coolingapparatus may include a casing portion having a coolant circulationportion and an outer edge portion surrounding the coolant circulationportion, where the coolant circulation portion is arranged under thelower surface of the top plate and the casing portion is closelyattached, directly or indirectly, to the lower surface of the top plateat the outer edge portion. The cooling apparatus may include a coolingfin arranged in the coolant circulation portion. The coolant circulationportion may have a first coolant flow channel and a second coolant flowchannel arranged, when seen from above in a perpendicular direction tothe lower surface of the top plate, so as to sandwich therebetween a finregion in which the cooling fin is provided, and each having two ends ina longitudinal direction. The casing portion may have a first openingprovided on an end side corresponding to a first end of the firstcoolant flow channel and to let a coolant in to or out of the firstcoolant flow channel. The casing portion may have a second openingprovided on an end side corresponding to a second end of the secondcoolant flow channel and to let a coolant in to or out of the secondcoolant flow channel. The second end and the first end may be arrangedon the same side of the casing portion. The first coolant flow channeland the second coolant flow channel may be each at least partly providedbelow the cooling fin. The first coolant flow channel and the secondcoolant flow channel may each have a flow channel bottom surface. Eachflow channel bottom surface may have an inclined portion, and a distancebetween a position on the inclined portion and the cooling fin in adepth direction perpendicular to the lower surface of the top platedecreases as a distance between the position on the inclined portion anda center of the fin region in a width direction parallel to the lowersurface of the top plate and perpendicular to the longitudinal directiondecreases.

The first coolant flow channel and the second coolant flow channel maybe provided below the cooling fin at least in an area facing, when seenfrom above, the semiconductor chip. The inclined portion may be providedat least in an area facing, when seen from above, the semiconductorchip.

A plurality of semiconductor chips, each semiconductor chip being thesemiconductor chip, may be provided at different positions in the widthdirection when seen from above. A center of a region in which theplurality of semiconductor chips are provided in the width direction maybe arranged closer to the first coolant flow channel than a center ofthe fin region in the width direction is located.

A first group of chips including a plurality of semiconductor chips,each semiconductor chip being the semiconductor chip, may be arrangedalong the first coolant flow channel in the longitudinal direction. Asecond group of chips including a plurality of semiconductor chips, eachsemiconductor chip being the semiconductor chip, may be arranged alongthe second coolant flow channel in the longitudinal direction. Adistance between the semiconductor chip arranged closest to the secondend in the second group of chips and the second end in the longitudinaldirection may be smaller than a distance between the semiconductor chiparranged closest to the first end in the first group of chips and thefirst end in the longitudinal direction.

The semiconductor device may have a circuit board to which a pluralityof semiconductor chips, each semiconductor chip being the semiconductorchip, are fixed. The circuit board may have a lead frame connected tothe semiconductor chip in the second group of chips. The circuit boardmay have a pad portion connected to the lead frame. The fin region maybe arranged so as to overlap the whole of the pad portion when seen fromabove.

At least one of the first coolant flow channel and the second coolantflow channel may be arranged so as to overlap the first group of chipsor the second group of chips when seen from above.

A distance between the first coolant flow channel and a center of thefin region in the width direction may be smaller than a distance betweenthe second coolant flow channel and a center of the fin region in thewidth direction.

The cooling fin may have a plurality of protruding portions extendingdownward from the top plate. At least some of the protruding portionsmay have a tapered portion, where an area of a cross section of thetapered portion parallel to the lower surface of the top plate decreasesaway from the top plate in a downward direction.

Among the plurality of protruding portions of the cooling fin, at leastsome of protruding portions which overlap the first coolant flow channelor the second coolant flow channel when seen from above may have thetapered portion, and protruding portions which do not overlap the firstcoolant flow channel or the second coolant flow channel when seen fromabove may not have the tapered portion.

According to the second aspect of the present invention, a coolingapparatus for a semiconductor module including a semiconductor chip isprovided. The cooling apparatus may include a casing portion having acoolant circulation portion and an outer edge portion surrounding thecoolant circulation portion, where the coolant circulation portion isarranged under the lower surface of the top plate, and the casingportion is closely attached, directly or indirectly, to the lowersurface of the top plate at the outer edge portion. The coolingapparatus may include a cooling fin arranged in the coolant circulationportion. The coolant circulation portion may have a first coolant flowchannel and a second coolant flow channel arranged, when seen from abovein a perpendicular direction to the lower surface of the top plate, soas to sandwich therebetween a fin region in which the cooling fin isprovided, and each having two ends in a longitudinal direction. Thecasing portion may have a first opening provided on an end sidecorresponding to a first end of the first coolant flow channel, and tolet a coolant in to or out of the first coolant flow channel. The casingportion may have a second opening provided on an end side correspondingto a second end of the second coolant flow channel, and to let a coolantin to or out of the second coolant flow channel. The second end and thefirst end may be arranged on the same side of the casing portion. Thefirst coolant flow channel and the second coolant flow channel may beeach at least partly provided below the cooling fin. The first coolantflow channel and the second coolant flow channel may each have a flowchannel bottom surface. Each flow channel bottom surface may have aninclined portion, and a distance between a position on the inclinedportion and the cooling fin in a depth direction perpendicular to thelower surface of the top plate decreases as a distance between theposition on the inclined portion and a center of the fin region in awidth direction parallel to the lower surface of the top plate andperpendicular to the longitudinal direction decreases.

According to the third aspect of the present invention, provided is avehicle including the semiconductor module according to the firstaspect.

The summary clause does not necessarily describe all necessary featuresof the embodiments of the present invention. The present invention mayalso be a sub-combination of the features described above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view schematically illustrating one exampleof a semiconductor module 100 according to one embodiment of the presentinvention.

FIG. 2 is a diagram illustrating an arrangement example of a cooling fin94, a first coolant flow channel 30-1, and a second coolant flow channel30-2 in the x-y plane.

FIG. 3 is a perspective view schematically illustrating a coolantcirculation portion 92.

FIG. 4 is a diagram illustrating end side regions 46.

FIG. 5 is a diagram illustrating an arrangement example of semiconductorchips 78 and a fin region 95.

FIG. 6 is a diagram illustrating an arrangement example of thesemiconductor chips 78 in the y-axis direction.

FIG. 7 is a diagram illustrating an arrangement example of a fin region95 and circuit elements provided on circuit boards 76.

FIG. 8 is a diagram illustrating an arrangement example of the circuitelements provided on the circuit boards 76 and a coolant flow channels30.

FIG. 9 is a cross-sectional view illustrating one example of protrudingportions 97 included in the cooling fin 94.

FIG. 10 illustrates an example in which flow velocities of a coolantflowing below the respective semiconductor chips 78 are compared.

FIG. 11 is a diagram schematically illustrating a vehicle 200 accordingto one embodiment of the present invention.

FIG. 12 is a main circuit diagram of a semiconductor module 100according to one embodiment of the present invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, the present invention will be described with reference toembodiments of the invention. However, the following embodiments shouldnot to be construed as limiting the claimed invention. Also, all thecombinations of the features described in the embodiments are notnecessarily essential for means provided by aspects of the invention.

FIG. 1 is a cross-sectional view schematically illustrating one exampleof a semiconductor module 100 according to one embodiment of the presentinvention. The semiconductor module 100 includes a semiconductor device70 and a cooling apparatus 10. The semiconductor device 70 in thepresent example is placed on the cooling apparatus 10. In thisspecification, the plane of the cooling apparatus 10 on which thesemiconductor device 70 is placed is defined as an x-y plane, and theaxis perpendicular to the x-y plane is defined as a z axis. In thisspecification, although the direction from the cooling apparatus 10toward the semiconductor device 70 in the z-axis direction is referredto as an upper direction and the direction opposite to the upperdirection is referred to as a lower direction, the upper and lowerdirections are not limited to the gravitational direction. Also, in thisspecification, the surface of surfaces of each member on the upper sideis referred to as an upper surface, the surface on the lower side isreferred to as a lower surface, and the surface between the uppersurface and the lower surface is referred to as a side surface.

The semiconductor device 70 includes one or more semiconductor chips 78such as a power semiconductor chip. As an example, an insulated gatebipolar transistor (IGBT) formed on a semiconductor substrate made ofsilicon or the like is provided on each semiconductor chip 78. In thesemiconductor chip 78, the insulated gate bipolar transistor and a freewheeling diode (FWD) may be provided on the same substrate.

The semiconductor device 70 has a circuit board 76 and an accommodatingportion 72. As an example, the circuit board 76 is a substrate with acircuit pattern provided on an insulating substrate. The semiconductorchips 78 are fixed on the circuit board 76 via solder or the like.

A pad portion 75 formed of a conductive material such as copper may beprovided on the circuit board 76. A lead frame 73 connecting thesemiconductor chip 78 with the pad portion 75 may be provided on thecircuit board 76. The lead frame 73 is a plate-shaped wiring formed of aconductive material such as aluminum. The lead frame 73 may be connectedto the semiconductor chip 78 and the pad portion 75 with solder or thelike. The pad portion 75 may be connected to other conductive memberswith a wire or the like.

The accommodating portion 72 is formed of an insulating material such asresin. The accommodating portion 72 has an internal space accommodatingthe semiconductor chips 78, the circuit board 76, the lead frame 73, andthe other circuit elements. The internal space of the accommodatingportion 72 may be filled with a sealing portion 74 sealing thesemiconductor chips 78, the circuit board 76, and the lead frame 73. Thesealing portion 74 is an insulating member such as silicone gel or epoxyresin to name a few.

The cooling apparatus 10 has a top plate 20 and a casing portion 40. Thetop plate 20 may be a plate-shaped metal plate having an upper surface22 and a lower surface 24 which are parallel to the x-y plane. The topplate 20 may have two short sides 26 facing each other and two longsides 28 facing each other. The short sides 26 may be parallel to thex-axis direction and the long sides may be parallel to the y-axisdirection. As an example, the top plate 20 is formed of a metalcontaining aluminum. The semiconductor device 70 is placed on the uppersurface 22 of the top plate 20. Heat generated by the semiconductorchips 78 is transferred to the top plate 20. For example, thermalconductive member such as the circuit board 76, a metal plate, andsolder are arranged between the top plate 20 and the semiconductor chip78. The circuit board 76 may be fixed directly on the upper surface 22of the top plate 20 with solder or the like. In this case, theaccommodating portion 72 is provided so as to surround the region inwhich the circuit board 76 and the like are arranged on the uppersurface 22 of the top plate 20. For other examples, the semiconductordevice 70 may have a metal plate exposed on the lower surface of theaccommodating portion 72, the circuit board 76 may be fixed on the uppersurface of the metal plate, and the metal plate may be fixed on theupper surface 22 of the top plate 20.

The casing portion 40 includes a coolant circulation portion 92 and anouter edge portion 41 surrounding the coolant circulation portion 92 inthe x-y plane. The coolant circulation portion 92 is arranged under thelower surface 24 of the top plate 20. The coolant circulation portion 92is a region in which a coolant such as water circulates. The coolantcirculation portion 92 may be a sealed space in contact with the lowersurface 24 of the top plate 20. Also, the casing portion 40 is closelyattached, directly or indirectly, to the lower surface 24 of the topplate 20 at the outer edge portion 41 surrounding the coolantcirculation portion 92 in the x-y plane. In this manner, the coolantcirculation portion 92 is sealed. Note that being closely attachedindirectly to each other refers to the state where the lower surface 24of the top plate 20 and the casing portion 40 are closely attached toeach other via a sealing material, an adhesive agent, or the othermembers provided between the lower surface 24 of the top plate 20 andthe casing portion 40. Being closely attached to each other refers tothe state where the coolant inside the coolant circulation portion 92does not leak from the closely attaching part. A cooling fin 94 isarranged inside the coolant circulation portion 92. The cooling fin 94may be connected to the lower surface 24 of the top plate 20. The heatgenerated by the semiconductor chips 78 is transferred to the coolant byallowing the coolant to pass through the vicinity of the cooling fin 94.In this manner, the semiconductor device 70 can be cooled.

The cooling fin 94 has a configuration in which columnar or plate-shapedstructures provided approximately perpendicular to the x-y plane may bearranged in the x-y plane in a predetermined pattern. For otherexamples, the cooling fin 94 has a configuration in which plate-shapedstructures which are provided approximately parallel to the x-y planeand are each provided with an opening serving as a flow channel for thecoolant may be stacked in the z-axis direction. Note that theconfiguration of the cooling fin 94 is not limited to theseconfigurations.

In this specification, the region in which the cooling fin 94 isprovided is referred to as a fin region 95. When seen from above, thefin region 95 may has a rectangular form, and may have two short sidesfacing each other and parallel to the x-axis direction and two longsides facing each other and parallel to the y-axis direction. The finregion 95 includes a region in which the structures of the cooling fin94 are provided and flow channels for the coolant formed between thestructures of the cooling fin 94.

The casing portion 40 in the present example has a frame portion 62 anda main-body portion 64. The outer edge portion 41 may include at leastthe frame portion 62. The frame portion 62 is arranged so as to surroundthe coolant circulation portion 92 in the x-y plane. The frame portion62 is closely attached, directly or indirectly, to the lower surface 24of the top plate 20. In other words, the frame portion 62 and the lowersurface 24 of the top plate 20 are provided so as to seal the coolantcirculation portion 92. A sealing material or other members may beprovided between the frame portion 62 and the lower surface 24 of thetop plate 20.

For the present example, the top plate 20 and the casing portion 40 arebrazed together. As an example, the top plate 20 is formed of a metalhaving the same composition as the metal the casing portion 40 is formedof, and the brazing material is formed of a metal having a lower meltingtemperature than the metal the top plate 20 and the like are formed of.As the metal, a metal containing aluminum may be used.

The main-body portion 64 is arranged so as to have the coolantcirculation portion 92 between the lower surface 24 of the top plate 20and the main-body portion 64. The frame portion 62 in the presentexample is a portion of the casing portion 40 closely attached to thelower surface 24 of the top plate 20, and the main-body portion 64 inthe present example is a portion of the casing portion 40 away from thelower surface 24 of the top plate 20. With the main-body portion 64being arranged away from the lower surface 24 of the top plate 20, thecoolant circulation portion 92 is formed.

The top plate 20 and the casing portion 40 are provided with throughholes 79 into which a screw or the like is inserted for fastening them.The through holes 79 may be also used to fix the semiconductor module100 to an external apparatus. The through holes 79 are provided in theregions in which the top plate 20 and the frame portion 62 are closelyattached, directly or indirectly, to each other and stacked in thez-axis direction.

The cooling fin 94 is arranged inside the coolant circulation portion92. An upper end of the cooling fin 94 may be connected to the lowersurface 24 of the top plate 20. A lower end 98 of the cooling fin 94 andthe main-body portion 64 may or may not be in contact with each other.

Inside the coolant circulation portion 92, a first coolant flow channel30-1 and a second coolant flow channel 30-2 are provided, which arearranged, when seen from above (when seen from above in the z-axisdirection perpendicular to the x-y plane, in the present example), so asto sandwich the cooling fin 94 therebetween. The first coolant flowchannel 30-1 and the second coolant flow channel 30-2 in the presentexample sandwich the cooling fin 94 therebetween in the x-axisdirection. Also, the respective coolant flow channels 30 extend alongthe cooling fin 94 in the y-axis direction (the longitudinal direction).

The main-body portion 64 is provided with openings 42 at the positionscorresponding to the respective coolant flow channels 30. One of theopenings 42 serves as an inlet to let the coolant in to the coolant flowchannel 30 and the other serves as an outlet to let the coolant out ofthe coolant flow channel 30. A user can appropriately select which ofthe openings 42 to use as which of the inlet and the outlet. Although afirst opening 42-1 corresponding to the first coolant flow channel 30-1serves as the inlet, and a second opening 42-2 corresponding to thesecond coolant flow channel 30-2 serves as the outlet in thisspecification, the functions of the respective openings 42 may bereversed.

The first coolant flow channel 30-1 and the second coolant flow channel30-2 are each at least partly provided below the cooling fin 94. Thecoolant flow channels 30 refer to spaces having a height (a length inthe z-axis direction) more than or equal to a predetermined heightinside the coolant circulation portion 92. The predetermined height maybe a distance between a lower end 98 of the cooling fin 94 and themain-body portion 64, at a center position 96 of the cooling fin 94 inthe x-y plane. In this regard, however, the flow channels formed betweenthe structures of the cooling fin 94 are not included in the coolantflow channels 30.

A space may be provided between the lower end 98 of the cooling fin 94and the main-body portion 64. In this manner, generation of stressesbetween the cooling fin 94 and the main-body portion 64 can be preventedeven if warpage or the like of the main-body portion 64 is generated.For other examples, the lower end 98 of the cooling fin 94 may be incontact with the main-body portion 64.

Each of the first coolant flow channel 30-1 and the second coolant flowchannel 30-2 has a flow channel bottom surface. The flow channel bottomsurface is a surface which is in contact with the coolant and facesupward. The flow channel bottom surface in the present example has aninclined portion 32 and a bottom portion 34. The smaller the distancebetween a position on the inclined portions 32 and the center position96 of the fin region 95 in the x-axis direction is, the smaller thedistance D1 between the position on the inclined portions 32 and thelower end 98 of the cooling fin 94 in the z-axis direction is. Forexample, the value of the z coordinate of a position on the inclinedportions 32-1, which is arranged on the negative side in the x-axisdirection and the negative side in the z-axis direction relative to thecooling fin 94, increases in the positive direction as the value of thex coordinate of the position increases in the positive direction. Also,the value of the z coordinate of a position on the inclined portions32-2, which is arranged on the positive side in the x-axis direction andthe negative side in the z-axis direction relative to the cooling fin94, increases in the positive direction as the value of the x coordinateof the position increases in the negative direction.

Also, the inclined portion 32 of each of the first coolant flow channel30-1 and the second coolant flow channel 30-2 is at least partlyprovided below the cooling fin 94. The inclined portion 32 of at leastone of the first coolant flow channel 30-1 and the second coolant flowchannel 30-2 may be wholly provided below the cooling fin 94. Also, eachof the openings 42 is arranged near the lower end of the inclinedportion 32 in the z-axis direction.

Providing the inclined portions 32 in this way enables the coolant letin through any one of the openings 42 to flow toward the lower end 98 ofthe cooling fin 94. Accordingly, the coolant can be efficientlydelivered to the region near the top plate 20 in the cooling fin 94, andthe semiconductor device 70 can be cooled efficiently.

In particular, when the space is provided between the lower end 98 ofthe cooling fin 94 and the main-body portion 64 as illustrated in FIG.1, the coolant flows into the space, resulting in low cooling efficiencyof the semiconductor device 70. With the present example, the coolantcan be delivered to the region near the top plate 20 to cool thesemiconductor device 70.

Note that a straight line 71 given by extending the inclined portion 32in the x-z cross section may intersect the semiconductor chip 78. Also,the straight line 71 may intersect the pad portion 75 connected to thesemiconductor chip 78 with the lead frame 73. In this manner, thecoolant easily flows toward the heat source, so that the semiconductordevice 70 can be cooled efficiently.

The bottom portion 34 is a surface connected to the inclined portion 32.The bottom portion 34 may be inclined relative to the x axis in thereverse direction to the direction in which the inclined portions 32 isinclined, or may be parallel to the x axis. Also, the main-body portion64 may have the side walls 36. Each of the side walls 36 connects thebottom portion 34 and the frame portion 62. The side walls 36 may beprovided so as to be parallel to the inclined portions 32 in the x-zplane. This makes it even easier for the coolant let in through theopening 42 to flow toward the lower end 98 of the cooling fin 94. Inthis regard, however, the side walls 36 may be provided so as to benonparallel to the inclined portions 32 in the x-z plane.

FIG. 2 is a diagram illustrating an arrangement example of the coolingfin 94, the first coolant flow channel 30-1, and the second coolant flowchannel 30-2 in the x-y plane. In FIG. 2, the first coolant flow channel30-1 and the second coolant flow channel 30-2 are projected on the planeparallel to the lower end 98 of the cooling fin 94 (A-A plane in FIG.1). In FIG. 2, the positions of the inclined portions 32 and the bottomportions 34 in the plane are illustrated with dotted lines. Also, thepositions of the side walls 36 in the plane are illustrated with solidlines. Although the cooling fin 94 illustrated in FIG. 2 has rod-shapedstructures arranged discretely in the x-y plane, the configuration ofthe cooling fin 94 is not so limited.

In this specification, each of the coolant flow channels 30 extendsalong the cooling fin 94 in the longitudinal direction (the y-axisdirection). Also, the direction parallel to the lower surface 24 of thetop plate 20 and perpendicular to the longitudinal direction (the y-axisdirection) is defined as the width direction (the x-axis direction). Thecooling fin 94 may be arranged such that the longitudinal direction ofthe fin region 95 is parallel to the y-axis direction. In other words,the longitudinal direction and the two long sides of the fin region 95may be mutually parallel.

Each of the coolant flow channels 30 has two ends 44 in the y-axisdirection. In FIG. 2, the first coolant flow channel 30-1 has a firstend 44-1 and a third end 44-3, and the second coolant flow channel 30-2has a second end 44-2 and a fourth end 44-4. The first end 44-1 and thesecond end 44-2 are ends on the same side, and the third end 44-3 andthe fourth end 44-4 are ends on the same side. The same side refers tothe relative positions of two ends 44 of one coolant flow channel inthey axis. For example, the first end 44-1 is arranged on the positiveside in the y-axis direction relative to the third end 44-3, and thesecond end 44-2 is arranged on the positive side in the y-axis directionrelative to the fourth end 44-4. In other words, the first end 44-1 andthe second end 44-2 are both arranged on the positive side in the y-axisdirection. When seen from above, the longitudinal directions of thefirst coolant flow channel 30-1 and the second coolant flow channel 30-2may be parallel to each other in the y-axis direction, and may beparallel also to the long sides of the fin region 95 and the long sidesof the top plate 20.

The first opening 42-1 is provided on an end side corresponding to thefirst end 44-1 of the first coolant flow channel 30-1. Also, the secondopening 42-2 is provided on an end side corresponding to the second end44-2 of the second coolant flow channel 30-2. In other words, the twoopenings 42 are provided, in the casing portion 40, on the same side ofthe coolant flow channels 30. A pipe 90 conveying the coolant isconnected to each of the openings 42. The range of “the end side” willbe described later.

As described in FIG. 1, each of the coolant flow channels 30 is arrangedso as to overlap the cooling fin 94. To be more specific, each of thecoolant flow channels 30 is arranged so as to have a predeterminedoverlap width W by which it overlaps the fin region 95 in the x-axisdirection over the entire length of the fin region 95 in the y-axisdirection illustrated with a dotted line in FIG. 2. The overlap width Wmay be constant regardless of position on the y axis, or may bedifferent depending on positions on the y axis. Also, the overlap widthW of the first coolant flow channel 30-1 may be the same as, or may bedifferent from the overlap width W of the second coolant flow channel30-2.

FIG. 3 is a perspective view schematically illustrating the coolantcirculation portion 92. As described in FIG. 1 and FIG. 2, the coolantcirculation portion 92 has the coolant flow channels 30 extending in they-axis direction at the both ends of the x-axis direction. Each of thecoolant flow channels 30 have the inclined portion 32, where the valueof the z coordinate of a position on the inclined portion 32 graduallyincreases from an outer side toward an inner side in the x-axisdirection. The outer side in the x-axis direction refers to the side farfrom the center of the coolant circulation portion 92 in the x-axisdirection, and the inner side refers to the side close to the center ofthe coolant circulation portion 92. The respective inclined portions 32in the example of FIG. 3 are provided so as to extend over the entirelength of the coolant circulation portion 92 in the y-axis direction.

FIG. 4 is a diagram illustrating end side regions 46. As describedabove, the first opening 42-1 is arranged on an end side region 46-1which is the region on the first end 44-1 side of the first coolant flowchannel 30-1. The second opening 42-2 is arranged on an end side region46-2 which is the region on the second end 44-2 side of the secondcoolant flow channel 30-2. The end side region 46-1 is a region of theregions obtained, for example, by quartering the first coolant flowchannel 30-1 in the y-axis direction that includes the first end 44-1.The end side region 46-2 is a region of the regions obtained, forexample, by quartering the second coolant flow channel 30-2 in they-axis direction that includes the second end 44-2. The openings 42 areeach provided on any surface of the main-body portion 64 surrounding theend side regions 46. The openings 42 may be provided on the surfaceapproximately parallel to the x-z plane as illustrated in FIG. 4, may beprovided on the surfaces approximately parallel to the x-y plane (i.e.,bottom surface), or may be provided on the surfaces approximatelyparallel to the y-z plane.

Also, in FIG. 4, the positions of the semiconductor chips 78 in the x-yplane are illustrated with solid lines. For the present example, theplurality of semiconductor chips 78 are arrayed in the y-axis directionalong the respective coolant flow channels 30. The end side region 46-1in the y-axis direction may extend from the position of thesemiconductor chip 78-1 arranged closest to the first end 44-1 in they-axis direction to the position of the first end 44-1 in the y-axisdirection. The end side region 46-2 in the y-axis direction may extendfrom the position of the semiconductor chip 78-4 arranged closest to thesecond end 44-2 in the y-axis direction to the position of the secondend 44-2 in the y-axis direction. The positions of the openings 42 mayoverlap the positions of the semiconductor chips 78 in the y-axisdirection.

Note that each of the coolant flow channels 30 is provided at least inan area facing, in the x-y plane, the semiconductor chips 78. In thepresent example, the area facing the semiconductor chips 78 includes thearea facing, in the x-axis direction, the semiconductor chips 78arranged on the both ends in the y-axis direction (for example, thesemiconductor chips 78-1 and 78-3 for the first coolant flow channel30-1) and the area facing, in the x-axis direction, the region locatedbetween these semiconductor chips 78. Similarly, the inclined portion 32is provided at least in an area facing, in the x-y plane, thesemiconductor chips 78. In this manner, efficient flow of the coolantcan be provided for the semiconductor chips 78 which generate heat. Inthe example illustrated in FIG. 4, the respective coolant flow channel30 and inclined portions 32 are provided so as to extend over the entirelength of the coolant circulation portion 92 in the y-axis direction.

FIG. 5 is a diagram illustrating an arrangement example of thesemiconductor chips 78 and the fin region 95. The structural featuresother than the arrangement of the semiconductor chips 78 and the finregion 95 are similar to those for the examples described in FIG. 1 toFIG. 4.

In the present example, the plurality of semiconductor chips 78 areprovided in different positions in the x-axis direction. As an example,the semiconductor chips 78-1, 78-2, and 78-3 are arranged at thedifferent positions in the x-axis direction from where the semiconductorchips 78-4, 78-5, and 78-6 are arranged. The region in which theplurality of the semiconductor chips 78 are provided is defined as achip region 80. The chip region 80 is a rectangular region having thesides parallel to the x axis and the sides parallel to the y axis thatcircumscribe the plurality of the semiconductor chips 78. The centralposition of the chip region 80 in the x-axis direction is a centerposition 82. Also, the central position of the fin region 95 in thex-axis direction is a center position 84.

In the present example, the center position 82 of the chip region 80 isarranged closer to the first coolant flow channel 30-1 than the centerposition 84 of the fin region 95 is located. Such an arrangement enablesthe semiconductor chips 78-4, 78-5, and 78-6 to be arranged closer tothe first coolant flow channel 30-1. When the coolant is let in from thefirst end 44-1 side and let out of the second end 44-2 side, thetemperature of the coolant in the region near the second end 44-2 isrelatively high. Therefore, heat emitted by the semiconductor chip 78-4or the semiconductor chip 78-5 near the second end 44-2 may not bedissipated sufficiently. With the arrangement in the present example,the semiconductor chip 78-4 and the semiconductor chip 78-5 can bearranged in the region in which the temperature of the coolant isrelatively low, promoting dissipation of heat emitted by thesemiconductor chip 78-4 or the semiconductor chip 78-5.

Note that a partial region of the semiconductor chip 78-4 which isclosest to the second end 44-2 may be arranged closer, in the x-axisdirection, to the first coolant flow channel 30-1 than the centerposition 84 of the fin region 95 is located. Also, a distance D2 betweenthe center position 84 of the fin region 95 and the first coolant flowchannel 30-1 in the x-axis direction may be smaller than or equal to thedistance D3 between the center position 84 and the second coolant flowchannel 30-2 in the x-axis direction. Also, the distance D2 may begreater than the distance D3. Note that the inclined portions 32 may beillustrated as the coolant flow channels 30 in the diagrams of FIG. 5and the like.

FIG. 6 is a diagram illustrating an arrangement example of thesemiconductor chips 78 in the y-axis direction. An arrangement of thesemiconductor chips 78 in the y-axis direction described in the presentexample may be applied to the respective aspects described in FIG. 1 toFIG. 5.

In the present example, the plurality of semiconductor chips 78-1, 78-2,and 78-3 arranged along the first coolant flow channel 30-1 in they-axis direction constitute a first group of chips 86-1. Also, theplurality of semiconductor chips 78-4, 78-5, and 78-6 arranged along thesecond coolant flow channel 30-2 in the y-axis direction constitute asecond group of chips 86-2.

The distance between the semiconductor chip 78-4 arranged closest to thesecond end 44-2 in the second group of chips 86-2 and the second end44-2 in the y-axis direction is defined as D4. Also, the distancebetween the semiconductor chip 78-1 arranged closest to the first end44-1 in the first group of chips 86-1 and the first end 44-1 in they-axis direction is defined as D5. In the present example, the distanceD4 is smaller than the distance D5. The flow velocity of the coolant isrelatively high in the vicinities of the first end 44-1 and the secondend 44-2 at which the openings 42 are provided. The flow velocity of thecoolant in the vicinity of the semiconductor chip 78-4 can be maderelatively high by reducing the distance D4 between the semiconductorchip 78-4 and the second end 44-2 in the y-axis direction as in thepresent example. Accordingly, heat from the semiconductor chip 78-4 iseasily dissipated.

FIG. 7 is a diagram illustrating an arrangement example of the finregion 95 and circuit elements provided on circuit boards 76. In thepresent example, the center position 82 of the chip region 80 isarranged closer to the first coolant flow channel 30-1 than the centerposition 84 of the fin region 95 is located, as illustrated in FIG. 5.

The semiconductor chips 78, the lead frames 73, and the pad portions 75are provided on the circuit boards 76 in the present example. The padportions 75 are pads connected to the semiconductor chips 78 via thelead frames 73. Therefore, heat from the semiconductor chips 78 areeasily transferred to the pad portions 75.

In the present example, the fin region 95 is arranged so as to overlapall of the pad portions 75, when seen from above. In this manner, heatfrom the pad portions 75 can be efficiently dissipated. Note that thecenter position 82 of the chip region 80 is arranged closer to the firstcoolant flow channel 30-1 than the center position 84 of the fin region95 is located, so that a vacant region is produced between thesemiconductor chips 78-4, 78-5, and 78-6 and the second coolant flowchannel 30-2 in the circuit boards 76. Arranging pad portions 75 in thevacant region makes it easy to arrange the pad portions 75 above the finregion 95 to cool the pad portions 75. One end of each of the leadframes 73 connected to the semiconductor chips 78-4, 78-5, and 78-6 maybe connected to each of the pad portions 75 arranged in the vacantregion.

FIG. 8 is a diagram illustrating an arrangement example of the circuitelements provided on the circuit boards 76 and the coolant flow channels30. At least one of the first coolant flow channel 30-1 and the secondcoolant flow channel 30-2 may be arranged so as to overlap the firstgroup of chips 86-1 or the second group of chips 86-2 when seen fromabove. In the example of FIG. 8, the first coolant flow channel 30-1partially overlaps the first group of chips 86-1. In this manner, thesemiconductor chips 78 in the first group of chips 86-1 can be cooledefficiently.

The second coolant flow channel 30-2 may be arranged so as to overlapthe pad portions 75 when seen from above as described in FIG. 7. The padportions 75 are pad portions 75 provided closer to the second coolantflow channel 30-2 than the semiconductor chip 78-4, 78-5, and 78-6. Thepad portions 75 may wholly overlap with the second coolant flow channel30-2 in the x-y plane. Also, the second coolant flow channel 30-2 mayoverlap the second group of chips 86-2 when seen from above.

Also, the pad portions 75 arranged so as to wholly overlap the coolantflow channel 30 may be greater in thickness in the z-axis direction thanthe other pad portions 75. This can improve the heat dissipationefficiency.

Also, the fin region 95 may have a tapered region, where the width ofthe tapered region in the x-axis direction decreases away from the firstend 44-1 and the second end 44-2 in the y-axis direction. In thismanner, in the region away from the first end 44-1 and the second end44-2, the resistance applied to the coolant by the cooling fin 94 can bereduced and a uniform flow velocity distribution of the coolant withinthe x-y plane can be provided.

FIG. 9 is a cross-sectional view illustrating one example of protrudingportions 97 included in the cooling fin 94. The cooling fin 94 in thepresent example includes the plurality of protruding portions 97extending downward from the top plate 20. The protruding portions 97 mayhave rod-shaped form or plate-shaped form. At least some of theprotruding portions 97-2 each have a tapered portion 99, where the areaof the cross section of the tapered portion 99 parallel to the lowersurface 24 of the top plate 20 decreases away from the top plate 20 inthe downward direction. The tapered portion 99 is provided in the regionincluding the lower end of the protruding portion 97. In the presentexample, the width of the tapered portion 99 in the x-axis directiondecreases away from the top plate 20 in the downward direction. Such aconfiguration enables the coolant flowing from below the cooling fin 94to flow to the vicinity of the lower surface 24 of the top plate 20efficiently.

At least some of the protruding portions 97 which overlap the firstcoolant flow channel 30-1 or the second coolant flow channel 30-2 whenseen from above may be the protruding portions 97-2 having the taperedportion 99. All of the protruding portions 97 which overlap the firstcoolant flow channel 30-1 and the second coolant flow channel 30-2 maybe the protruding portions 97-2.

The protruding portions 97 which do not overlap the first coolant flowchannel 30-1 or the second coolant flow channel 30-2 when seen fromabove may be the protruding portions 97-1 which do not have the taperedportion 99. As an example, the cross-sectional area of the protrudingportion 97-1 at its lower end is the same as the cross-sectional area atits upper end in contact with the top plate 20.

In this manner, the coolant can flow to the vicinity of the top plate 20in the region overlapping the coolant flow channels 30. Also, thecoolant easily flows in the direction approximately parallel to thelower surface 24 of the top plate 20 in the region not overlapping thecoolant flow channels 30. Note that the length of the protruding portion97-2 having the tapered portion 99 in the z-axis direction, L2, may bethe same as or longer than the length of the protruding portion 97-1 inthe z-axis direction, L1.

FIG. 10 illustrates an example in which flow velocities of the coolantflowing below the respective semiconductor chips 78 are compared. InFIG. 10, the graphs hatched with oblique lines indicate flow velocitiesin a comparative example, while the graphs without the hatching indicatethe flow velocities for the arrangement of the semiconductor chips 78illustrated in FIG. 5. In the comparative example, the center position84 of the fin region 95 and the center position 82 of the chip region 80are located at the same position.

As illustrated in FIG. 10, the flow velocity around the semiconductorchip 78-4, where heat from the semiconductor chip 78-4 is relativelydifficult to dissipate, can be improved by making the center position 84of the fin region 95 different from the center position 82 of the chipregion 80. Therefore, the semiconductor chip 78-4 can be cooledefficiently, and the thermal distribution in the x-y plane can be madeuniform.

Note that, in the examples described in FIG. 1 to FIG. 9, the depth ofthe first coolant flow channel 30-1 in the z-axis direction may be thesame as or different from the depth of the second coolant flow channel30-2 in the z-axis direction. Also, the depth of each of the coolantflow channels 30 in the z-axis direction may change depending on thepositions in the y-axis direction.

FIG. 11 is a diagram schematically illustrating a vehicle 200 accordingto one embodiment of the present invention. A vehicle 200 is a vehiclewhich uses electrical power to generate at least part of thrust. As anexample, the vehicle 200 is an electric vehicle in which a power-drivendevice such as a motor generates all of thrust, or a hybrid vehiclewhich uses a power-driven device such as a motor in conjunction with aninternal combustion engine driven by fuel such as gasoline.

The vehicle 200 includes a control apparatus 210 (an external apparatus)configured to control the power-driven device such as a motor. Thesemiconductor module 100 is provided in the control apparatus 210. Thesemiconductor module 100 may control electrical power to be supplied tothe power-driven device.

FIG. 12 is a main circuit diagram of the semiconductor module 100according to one embodiment of the present invention. The semiconductormodule 100 may constitute a part of an in-vehicle unit configured todrive the motor of a vehicle. The semiconductor module 100 may serve asa three-phase alternating current inverter circuit having outputterminals U, V, and W.

Semiconductor chips 78-1, 78-2, and 78-3 may constitute an upper arm ofthe semiconductor module 100, and semiconductor chips 78-4, 78-5, and78-6 may constitute a lower arm of the semiconductor module 100. A pairof semiconductor chips 78-1, 78-4 may constitute a leg. Similarly, apair of semiconductor chips 78-2, 78-5 may constitute a leg and a pairof semiconductor chips 78-3, 78-6 may constitute a leg. The emitterelectrode and the collector electrode of the semiconductor chip 78-6 maybe electrically connected to an input terminal N1 and an output terminalU, respectively. The emitter electrode and the collector electrode ofthe semiconductor chip 78-3 may be electrically connected to the outputterminal U and an input terminal P1, respectively. Similarly, theemitter electrode and the collector electrode of the semiconductor chip78-5 may be electrically connected to an input terminal N2 and an outputterminal V, respectively, and the emitter electrode and the collectorelectrode of the semiconductor chip 78-4 may be electrically connectedto an input terminal N3 and an output terminal W, respectively. Further,the emitter electrode and the collector electrode of the semiconductorchip 78-2 may be electrically connected to the output terminal V and aninput terminal P2, respectively, and the emitter electrode and thecollector electrode of the semiconductor chip 78-1 may be electricallyconnected to the output terminal W and an input terminal P3,respectively.

Each of the semiconductor chips 78-1 to 78-6 may be alternately switchedon and off by the signal input into the control electrode pads of thesemiconductor chips 78. Each of the semiconductor chips 78 in thepresent example may generate heat at the time of switching. The inputterminals P1, P2, and P3 may be connected to the positive side of theexternal power source, the input terminals N1, N2, and N3 to thenegative side of the external power source, and the output terminals U,V, and W to a load, respectively. The input terminals P1, P2, and P3 maybe electrically connected to one another, and the other input terminalsN1, N2, and N3 may be also electrically connected to one another.

The plurality of semiconductor chips 78-1 to 78-6 of the semiconductormodule 100 may each be an RC-IGBT (Reverse Conducting IGBT)semiconductor chip. In the RC-IGBT semiconductor chip, an IGBT and afree wheeling diode (FWD) are integrally formed, and the IGBT and theFWD may be connected in inverse parallel. The plurality of semiconductorchips 78-1 to 78-6 may each include a combination of a transistor suchas MOSFET or IGBT and a diode. The chip substrates for the transistorand the diode may be a silicon substrate, a silicon carbide substrate,or a gallium nitride substrate.

While the embodiments of the present invention have been described, thetechnical scope of the invention is not limited to the above describedembodiments. It is apparent to persons skilled in the art that variousalterations and improvements can be added to the above-describedembodiments. It is also apparent from the scope of the claims that theembodiments added with such alterations or improvements can be includedin the technical scope of the invention.

The operations, procedures, steps, and stages of each process performedby an apparatus, system, program, and method shown in the claims,embodiments, or diagrams can be performed in any order as long as theorder is not indicated by “prior to,” “before,” or the like and as longas the output from a previous process is not used in a later process.Even if the process flow is described using phrases such as “first” or“next” in the claims, embodiments, or diagrams, it does not necessarilymean that the process must be performed in this order.

What is claimed is:
 1. A semiconductor module comprising a coolingapparatus and a semiconductor device, wherein the semiconductor deviceincludes a semiconductor chip, the cooling apparatus includes: a topplate having an upper surface and a lower surface, the semiconductorchip being arranged above the upper surface; a casing portion having acoolant circulation portion and an outer edge portion surrounding thecoolant circulation portion, the coolant circulation portion beingarranged under the lower surface of the top plate, and the casingportion being closely attached, directly or indirectly, to the lowersurface of the top plate at the outer edge portion; and a cooling finarranged in the coolant circulation portion, the coolant circulationportion has a first coolant flow channel and a second coolant flowchannel arranged, when seen from above in a perpendicular direction tothe lower surface of the top plate, so as to sandwich therebetween a finregion in which the cooling fin is provided, and each having two ends ina longitudinal direction, the longitudinal direction being parallel to aboundary between the fin region and each coolant flow channel, thecasing portion includes: a first opening provided on an end sidecorresponding to a first end of the first coolant flow channel, and tolet a coolant in to or out of the first coolant flow channel; and asecond opening provided on an end side corresponding to a second end ofthe second coolant flow channel, the second end and the first end beingarranged on the same side of the casing portion, and the second openingto let a coolant in to or out of the second coolant flow channel, thefirst coolant flow channel and the second coolant flow channel are eachat least partly provided below the cooling fin, the first coolant flowchannel and the second coolant flow channel each have a flow channelbottom surface, each flow channel bottom surface has an inclinedportion, and a distance between a position on the inclined portion andthe cooling fin in a depth direction perpendicular to the lower surfaceof the top plate decreases as a distance between the position on theinclined portion and a center of the fin region in a width directionparallel to the lower surface of the top plate and perpendicular to thelongitudinal direction decreases, and a distance between an upper end ofthe inclined portion of the first coolant flow channel and the center ofthe fin region in the width direction is smaller than a distance betweenan upper end of the inclined portion of the second coolant flow channeland the center of the fin region in the width direction.
 2. Thesemiconductor module according to claim 1, wherein the first coolantflow channel and the second coolant flow channel are provided below thecooling fin at least in an area facing, when seen from above, thesemiconductor chip, and the inclined portion is provided at least in anarea facing, when seen from above, the semiconductor chip.
 3. Thesemiconductor module according to claim 1, wherein a plurality ofsemiconductor chips are provided at different positions in the widthdirection when seen from above, each semiconductor chip being thesemiconductor chip and a center of a region in which the plurality ofsemiconductor chips are provided in the width direction is arrangedcloser to the first coolant flow channel than a center of the fin regionin the width direction is located.
 4. The semiconductor module accordingto claim 3, wherein a first group of chips including a plurality ofsemiconductor chips is arranged along the first coolant flow channel inthe longitudinal direction, each semiconductor chip being thesemiconductor chip, a second group of chips including a plurality ofsemiconductor chips is arranged along the second coolant flow channel inthe longitudinal direction, each semiconductor chip being thesemiconductor chip and a distance between the semiconductor chiparranged closest to the second end in the second group of chips and thesecond end in the longitudinal direction is smaller than a distancebetween the semiconductor chip arranged closest to the first end in thefirst group of chips and the first end in the longitudinal direction. 5.The semiconductor module according to claim 4, wherein the semiconductordevice has a circuit board to which a plurality of semiconductor chips,each semiconductor chip being the semiconductor chip, are fixed, thecircuit board has: a lead frame connected to the semiconductor chip inthe second group of chips; and a pad portion connected to the leadframe, and the fin region is arranged so as to overlap the whole of thepad portion when seen from above.
 6. The semiconductor module accordingto claim 4, wherein at least one of the first coolant flow channel andthe second coolant flow channel is arranged so as to overlap the firstgroup of chips or the second group of chips when seen from above.
 7. Thesemiconductor module according to claim 1, wherein the cooling fin has aplurality of protruding portions extending downward from the top plate,and at least some of the protruding portions have a tapered portion, andan area of a cross section of the tapered portion parallel to the lowersurface of the top plate decreases away from the top plate in a downwarddirection.
 8. A vehicle comprising the semiconductor module according toclaim
 1. 9. The semiconductor module according to claim 1, wherein theinclined portion of each flow channel bottom surface extends over theentire length of the coolant circulation portion in the longitudinaldirection.
 10. A semiconductor module comprising a cooling apparatus anda semiconductor device, wherein the semiconductor device includes asemiconductor chip, the cooling apparatus includes: a top plate havingan upper surface and a lower surface, the semiconductor chip beingarranged above the upper surface; a casing portion having a coolantcirculation portion and an outer edge portion surrounding the coolantcirculation portion, the coolant circulation portion being arrangedunder the lower surface of the top plate, and the casing portion beingclosely attached, directly or indirectly, to the lower surface of thetop plate at the outer edge portion; and a cooling fin arranged in thecoolant circulation portion, the coolant circulation portion has a firstcoolant flow channel and a second coolant flow channel arranged, whenseen from above in a perpendicular direction to the lower surface of thetop plate, so as to sandwich therebetween a fin region in which thecooling fin is provided, and each having two ends in a longitudinaldirection, the longitudinal direction being parallel to a boundarybetween the fin region and each coolant flow channel, the casing portionincludes: a first opening provided on an end side corresponding to afirst end of the first coolant flow channel, and to let a coolant in toor out of the first coolant flow channel; and a second opening providedon an end side corresponding to a second end of the second coolant flowchannel, the second end and the first end being arranged on the sameside of the casing portion, and the second opening to let a coolant into or out of the second coolant flow channel, the first coolant flowchannel and the second coolant flow channel are each at least partlyprovided below the cooling fin, the first coolant flow channel and thesecond coolant flow channel each have a flow channel bottom surface,each flow channel bottom surface has an inclined portion, and a distancebetween a position on the inclined portion and the cooling fin in adepth direction perpendicular to the lower surface of the top platedecreases as a distance between the position on the inclined portion anda center of the fin region in a width direction parallel to the lowersurface of the top plate and perpendicular to the longitudinal directiondecreases, the cooling fin has a plurality of protruding portionsextending downward from the top plate, at least some of the protrudingportions have a tapered portion, and an area of a cross section of thetapered portion parallel to the lower surface of the top plate decreasesaway from the top plate in a downward direction, and among the pluralityof protruding portions of the cooling fin, at least some of protrudingportions which overlap the first coolant flow channel or the secondcoolant flow channel when seen from above have the tapered portion, andprotruding portions which do not overlap the first coolant flow channelor the second coolant flow channel when seen from above do not have thetapered portion.
 11. A cooling apparatus for a semiconductor moduleincluding a semiconductor chip, comprising: a top plate having a lowersurface; a casing portion having a coolant circulation portion and anouter edge portion surrounding the coolant circulation portion, thecoolant circulation portion being arranged under the lower surface ofthe top plate, and the casing portion being closely attached, directlyor indirectly, to the lower surface of the top plate at the outer edgeportion; and a cooling fin arranged in the coolant circulation portion,wherein the coolant circulation portion has a first coolant flow channeland a second coolant flow channel arranged, when seen from above in aperpendicular direction to the lower surface of the top plate, so as tosandwich therebetween a fin region in which the cooling fin is provided,and each having two ends in a longitudinal direction, the longitudinaldirection being parallel to a boundary between the fin region and eachcoolant flow channel, the casing portion includes: a first openingprovided on an end side corresponding to a first end of the firstcoolant flow channel, and to let a coolant in to or out of the firstcoolant flow channel; and a second opening provided on an end sidecorresponding to a second end of the second coolant flow channel, thesecond end and the first end being arranged on the same side of thecasing portion, and the second opening to let a coolant in to or out ofthe second coolant flow channel, the first coolant flow channel and thesecond coolant flow channel are each at least partly provided below thecooling fin, the first coolant flow channel and the second coolant flowchannel each have a flow channel bottom surface, each flow channelbottom surface has an inclined portion, and a distance between aposition on the inclined portion and the cooling fin in a depthdirection perpendicular to the lower surface of the top plate decreasesas a distance between the position on the inclined portion and a centerof the fin region in a width direction parallel to the lower surface ofthe top plate and perpendicular to the longitudinal direction decreases,and a distance between an upper end of the inclined portion of the firstcoolant flow channel and the center of the fin region in the widthdirection is smaller than a distance between an upper end of theinclined portion of the second coolant flow channel and the center ofthe fin region in the width direction.
 12. A cooling apparatus for asemiconductor module including a semiconductor chip, comprising: a topplate having a lower surface; a casing portion having a coolantcirculation portion and an outer edge portion surrounding the coolantcirculation portion, the coolant circulation portion being arrangedunder the lower surface of the top plate, and the casing portion beingclosely attached, directly or indirectly, to the lower surface of thetop plate at the outer edge portion; and a cooling fin arranged in thecoolant circulation portion, wherein the coolant circulation portion hasa first coolant flow channel and a second coolant flow channel arranged,when seen from above in a perpendicular direction to the lower surfaceof the top plate, so as to sandwich therebetween a fin region in whichthe cooling fin is provided, and each having two ends in a longitudinaldirection, the longitudinal direction being parallel to a boundarybetween the fin region and each coolant flow channel, the casing portionincludes: a first opening provided on an end side corresponding to afirst end of the first coolant flow channel, and to let a coolant in toor out of the first coolant flow channel; and a second opening providedon an end side corresponding to a second end of the second coolant flowchannel, the second end and the first end being arranged on the sameside of the casing portion, and the second opening to let a coolant into or out of the second coolant flow channel, the first coolant flowchannel and the second coolant flow channel are each at least partlyprovided below the cooling fin, the first coolant flow channel and thesecond coolant flow channel each have a flow channel bottom surface,each flow channel bottom surface has an inclined portion, and a distancebetween a position on the inclined portion and the cooling fin in adepth direction perpendicular to the lower surface of the top platedecreases as a distance between the position on the inclined portion anda center of the fin region in a width direction parallel to the lowersurface of the top plate and perpendicular to the longitudinal directiondecreases, the cooling fin has a plurality of protruding portionsextending downward from the top plate, at least some of the protrudingportions have a tapered portion, and an area of a cross section of thetapered portion parallel to the lower surface of the top plate decreasesaway from the top plate in a downward direction, and among the pluralityof protruding portions of the cooling fin, at least some of protrudingportions which overlap the first coolant flow channel or the secondcoolant flow channel when seen from above have the tapered portion, andprotruding portions which do not overlap the first coolant flow channelor the second coolant flow channel when seen from above do not have thetapered portion.